BONE S 33 



injuring it; and the bottom of the chest-cavity is so nar- 

 rowed that the heart and lungs are cramped for room. 



12. What should be Done when a Bone is Broken. When 

 a bone is broken, it is said to be fractured. The muscles 

 on each side of the break are very apt to pull the pieces 

 of the bone out of place. Therefore the broken bone 

 needs to be set into place, and then held by splints and 

 bandages so that the ends be kept together until they 

 unite. To set a broken bone, often needs great skill and 

 a thorough knowledge of anatomy. A medical man 

 should be summoned without delay, as the parts around 

 the fracture usually swell very rapidly, making the 

 exact position of the break hard to find out, and the re- 

 placement of the pieces of the bone more difficult. Until 

 skilled aid arrives, the sufferer should be kept as quiet 

 as possible: cloths dipped in cold water and frequently 

 renewed may be applied to keep down swelling and in- 

 flammation. 



13. How a Broken Bone is Knit together again. A 

 watery liquid first collects between and around the 

 broken ends. This gradually thickens, becoming jelly- 

 like, and then of the hardness of gristle, though it does 

 not become actual cartilage. It is chiefly made by 

 the periosteum, which becomes very active where the 

 bone is broken, and makes this uniting material in such 

 abundance that it forms quite a thick ring all round 

 the fracture. This ring, named the callus, is afterwards 



12. What is a fracture ? Why does a broken bone require to be 

 set ? Why should a doctor be summoned at once ? What should be 

 done until he arrives ? 



13. What first happens when Nature begins to repair a broken 

 bone? Next? What makes this first uniting material ? What is the 

 callus ? Its use ? What finally becomes of it ? What takes place 

 inside the callus? 



